横向腹板加劲肋的合理设计模型

腹板加劲肋的现行设计方法在概念和加劲肋尺寸上有很大差异。为了给横向加劲肋提出一个合理、适用的有效设计方法,考虑了加劲肋上由拉力和外力作用产生的轴向压力,加劲肋上有效分隔腹板所必需的横向力和加劲板的整体屈曲趋势。为保证加劲肋的屈服不会在板屈服前发生,建立了相应的设计标准。     

Static tests on steel-concrete-steel sandwich beams

Bi-Steel is an innovative form of steel-concrete-steel sandwich construction invented by Bowerman [Bowerman H, Coyle N, Chapman JC. An innovative steel/concrete construction system. The Structural Engineer 2002;80(20):33-8], in which the two steel plates are inter-connected by a series of transverse bar connectors simultaneously friction welded at both ends. In use, the steel units are assembled, welded, and filled with concrete. The behaviour of the friction-welded bar-plate connections embedded in concrete subjected to bar tension and bar shear have been described in papers [Xie M, Chapman JC. Static and fatigue tensile strength of friction-welded bar-plate connections embedded in concrete. Journal of Constructional Steel Research 2005;61:651-73; Xie M, Foundoukos N, Chapman JC. Experimental and numerical investigation on the shear behaviour of friction-welded bar-plate connections embedded in concrete. Journal of Constructional Steel Research 2005;61:625-49]. This paper presents an experimental investigation on the static behaviour of Bi-Steel beams. Eighteen beams having a range of span, depth, plate thickness and bar spacing, have been tested under static loading, and four elementary modes of failure were observed: tension plate yielding, bar shear, bar tension and concrete shear. The tests confirm that for ductile failure, beams should be designed to fail by yielding of the tension plate. Comparisons are made with current design recommendations and some alternative methods are proposed.     

Fatigue tests on steel-concrete-steel sandwich components and beams

In Bi-Steel steel-concrete-steel sandwich members, the friction welded bar-plate connections are subject to plate tension, bar tension and bar shear with associated bar bending. The relative magnitude of these force components depends on the beam geometry and the type of loading. The force components interact, so component fatigue tests were performed under single and combined loads, each with a sufficient number of stress ranges to enable stress vs. fatigue life (S/N) curves and equations to be defined. Fatigue tests were also conducted on eighteen beams, and the experimental fatigue lives are compared with the values estimated by means of a proposed interaction equation based on the experimental S/N equations derived from the component tests.     

A finite element model based on coupled refined high-order global-local theory for static analysis of electromechanical embedded shear-mode piezoelectric sandwich composite beams with various widths

In this study, a new theory for the accurate simulation of the shear-mode behaviour of thin or thick piezoelectric sandwich composite beams is developed. The effects of transverse normal stress and transverse flexibility of layers are considered in the development of the proposed formulation. In order to increase the computational accuracy, all kinematic and stress continuity conditions are satisfied at layer interfaces. Moreover, for the first time, both the electrically induced strain components and the transverse flexibility are taken into account in the proposed formulation. Despite the fact that the number of unknown mechanical parameters in this theory is only one degree higher than the first order shear deformation theory, the accuracy is surprisingly more pronounced for the thicker beams.     

Finite element modeling of block shear failure in coped steel beams

Block shear is a potential failure mode that is encountered in the connection regions of coped steel beams. Limited experimental studies completed so far have shown that the block shear failure in coped steel beams is a complex phenomenon, which is highly dependent on the number of bolt lines. In this paper, the use of the finite element method in predicting the block shear failure load was studied by making comparisons with experimental findings. The effects of numerical modeling details on load capacity predictions were investigated. In light of these investigations, a finite element analysis methodology has been developed and used to conduct a parametric study. Simplified load capacity prediction equations were developed based on the results of the parametric study and are presented herein.     

Finite element modelling of composite beams with full and partial shear connection

The present investigation focuses on the evaluation of full and partial shear connection in composite beams using the commercial finite element (FE) software ANSYS. The proposed three-dimensional FE model is able to simulate the overall flexural behaviour of simply supported composite beams subjected to either concentrated or uniformly distributed loads. This covers: load deflection behaviour, longitudinal slip at the steel-concrete interface, distribution of stud shear force and failure modes. The reliability of the model is demonstrated by comparisons with experiments and with alternative numerical analyses. This is followed by an extensive parametric study using the calibrated FE model. The paper also discusses in detail several numerical modelling issues related to potential convergence problems, loading strategies and computer efficiency. The accuracy and simplicity of the proposed model make it suitable to predict and/or complement experimental investigations.     

A refined mixed global–local finite element model for bending analysis of multi-layered rectangular composite beams with small widths

A refined global–local finite element model is presented based on a mixed C¹-continous formulation for bending analysis of laminated composite rectangular beams with small widths. Formulation of the present beam element that is free of shear locking, ensures continuity conditions of the displacements and transverse shear stresses at the interfaces, satisfies the non-homogenous shear tractions on the upper and lower surfaces of the beam, and its number of unknowns is independent of the number of layers. Comparisons made with previous results and results of the 3D theory of elasticity confirm accuracy of the presented formulation for the thin and relatively thick beams.     

基于ANSYS的碳纤维布加固混凝土梁有限元分析

碳纤维布具有耐腐蚀、施工简便快速等诸多的优点,在土木工程中得到了较为广泛的应用。应用ANSYS软件对未加固梁和5根碳纤维布混凝土梁梁体受弯进行了仿真研究,并给出了相应的荷载挠度曲线。与试验结果对比表明,建立的有限元模型能较好地模拟碳纤维布混凝土梁的力学性能,非线性有限元模拟结果与试验结果基本吻合。     

Out-of-plane behaviour of partially composite or sandwich beams by exact and Finite Element Methods

The out-of-plane vibrations of composite beams with interlayer slip or three-layer sandwich beams are theoretically and numerically investigated in this paper for general boundary conditions. The governing dynamics equations are derived by applying the Hamilton's principle. A Finite Element Resolution is presented for general boundary conditions, and compared to the exact solution based on the resolution of a tenth-order differential equation. The Finite Element Method may exhibit slip locking phenomenon for very stiff connection, a phenomenon widely investigated in the past for the in-plane behaviour of partially composite beams or sandwich beams. This slip locking, analogous to the shear locking for Timoshenko beams, can be faced with some relevant interpolation shape functions of the same order for each kinematics variables, namely the deflections and the torsion angle. The numerical results are presented for layered wood beams and laminated glass beams, with particular emphasis on the rate of convergence of the natural frequencies with respect to the number of Finite Elements. It is theoretically and numerically shown that the elastic spectra of the symmetrical composite beam are composed of two independent spectrums. One spectrum is independent of the connection parameter and can be studied using the solution of the non-composite action, whereas the second spectrum can be obtained from the resolution of a third-order polynomial equation using the Cardano's method. We show the phenomenon of cut-on frequency for this out-of-plane problem, a phenomenon already noticed for the in-plane Timoshenko beam vibrations. The exact method associated to a 10 degrees-of-freedom shape function can be formally associated with the dynamics stiffness method. The numerical and the exact approaches lead to the same dimensionless spectra, up to four digits.     

Assessment of various kinematic models for instability analysis of sandwich beams

The aim of this paper is to present and compare various one-dimensional (1D) finite element (FE) models which are based on different kinematic models. The kinematic models presented take into account thickness variations, but differ in the inclusion of the shear deformation effects in their kinematics formulations. These 1D FE models are used to study global and local instability phenomenon in sandwich beams. Simulations of the buckling and three-point bending tests are performed to verify the capability of each model to reproduce the linear and nonlinear mechanical response of sandwich beams. The predicted results using 1D FE models are compared to a two-dimensional (2D) FE analysis, which is considered as a reference solution.     

Evaluation of the transverse shear stiffness of a steel bi-directional corrugated-strip-core sandwich beam

This paper presents a new concept in steel bi-directional corrugated-core sandwich structures. The focus is on the derivation of the transverse shear stiffness D_Qy of a sandwich beam using analytical methods. A braced frame analogy and its periodical unit cell, based on a force-distortion relationship concept, are used as the basis for deriving transverse shear stiffness relationships using the modified stiffness matrix approach. The transverse shear stiffness equation is consistent with a three-dimensional finite element solution. It is then used to assess the effect of geometrical parameters defining the corrugated sandwich beam. The performance of a steel bi-directional corrugated-strip-core sandwich beam compared with other corrugated-like core sandwich beams is then examined and discussed.     

钢—混凝土组合梁单调静力性能有限元分析

利用ANSYS软件建立了钢—混凝土组合梁的有限元模型,并对其进行了非线性分析,通过与试验结果的对比验证了建模方法的正确性,在此基础上,分析了栓钉间距、有效预应力等参数对钢—混凝土组合梁静力性能的影响,以期为钢—混凝土组合梁的设计计算提供指导。     

预应力碳纤维布加固混凝土梁有限元分析

利用碳纤维布(CFRP)加固钢筋混凝土构件是一种先进的工程加固技术,已经在土木工程中得到了较为广泛的应用。本文应用ANSYS软件对碳纤维加固预应力和非预应力梁体受弯进行仿真,来分析和研究碳纤维加固混凝土梁的受力机理和加固效果,并给出了相应的荷载挠度曲线。结果表明应用预应力碳纤维的梁体明显优于普通碳纤维布加固的受损梁,不仅提高了结构各阶段的承载力而且降低了梁破坏时的挠度。     

Nonlinear analysis of composite beams subjected to combined flexure and torsion

There are situations in which a composite steel-concrete beam is subjected to torsion, such as members that are curved in plan or straight edge beams in buildings or bridges. The composite action of the steel beam and concrete slab in torsion is usually ignored in design codes of practice. Therefore, a three-dimensional (3D) finite element model is introduced in this paper to simulate composite steel-concrete beams subjected to combined flexure and torsion with the influence of partial shear connection using a commercial software ABAQUS. Brick and truss elements were used with the incorporation of nonlinear material characteristics and geometric behaviour in the model. This is coupled with an extensive parametric study using the validated finite element model using different parameters such as the span length and the level of shear connection. From the analytical study, a new phenomenon has been uncovered, which was validated by the test observation. This phenomenon called torsion induced vertical slip is an important issue, which would make the assumption plane sections remain plane invalid. In addition, difference in span length greatly affected the flexure-torsion interaction relationship of the composite steel-concrete beams, whilst the partial shear connection did not affect the relationship. Design models for readers to take away at the end of this paper are also proposed.     

基于细分的整体-局部混合有限元模型的多层薄腹矩形组合梁的弯矩分析

基于混合C1-连续方程,建立细分的整体-局部有限元模型并进行多层薄腹矩形组合梁的抗弯分析。梁单元不考虑剪切闭锁,保证层交接面位移和横向剪切应力传递的连续性,并满足上下交接面非均匀剪应力轨迹线,其数目与层数无关。将已有结果与3D弹性理论的分析结果对比,证实本方程对薄腹梁的准确性。     

Finite element analysis of shear deformation in reinforced concrete shear-critical beams

The objective of this paper was to study the contribution of shear deformation in reinforced concrete (RC) shear-critical beams. A 2D concrete material model based on smeared fixed crack was presented and incorporated into a commercial finite element (FE) software. A method of calculating shear and flexure deformation separately out of total deformation in the shear span was presented and implemented into the FE analysis. Several experiments of RC shear-critical beams were simulated and good agreement between the experimental and numerical results was obtained in terms of total deformation, flexure deformation, shear deformation and crack patterns. The results show that after shear cracking, the contribution of shear deformation to total deformation increases rapidly. The shear span-to-depth ratio, the longitudinal reinforcement, the shear reinforcement and the load level could be the critical factor to influence the contribution of shear deformation. It appears that for RC shear-critical beams without shear reinforcement, the deformational behaviour is governed by flexure deformation. However, for RC beams with shear reinforcement, the contribution of shear deformation is not negligible after shear cracks develop. Moreover, the measuring method could also affect the measured shear deformation. Finally, future work on experimental investigation into this topic is recommended.     

A large deformation–small strain formulation for the mechanics of geometrically exact thin-walled composite beams

This work presents a new formulation of the geometrically exact thin walled composite beam theory. The formulation assumes that the beam can undergo arbitrary kinematical changes while the strains remain small, thus compatibilizing the hypotheses of the strain measure and the constitutive law of the composite material. A key point of the formulation is the development of a pure small strain measure written solely in terms of scalar products of position and director vectors; the latter is accomplished through the obtention of a generalized small strain vector by decomposition of the deformation gradient. The resulting small strain measure is objective under rigid body motion. The finite element implementation of the proposed formulation is simpler than the finite strain theory implementation previously developed by the authors. Numerical experiments show that the present formulation is very accurate and computationally more efficient than the finite strain formulation, thus it is more convenient for most practical applications.     

An isogeometric approach for the analysis of composite steel–concrete beams

An isogeometric approach based on non-uniform rational B-spline (NURBS) basis functions is presented for the analysis of composite steel–concrete beams. A refined high-order theory is considered in deriving the governing equations using the principle of virtual work. The employed theory satisfies all the kinematic and stress continuity conditions at the layer interfaces and considers effects of the transverse normal stress and transverse flexibility. The global displacement components, described by polynomial or combinations of polynomial and exponential expressions, are superposed on local ones chosen based on the layerwise concepts. The present isogeometric formulation does not need incorporating any shear correction factor. Moreover, in the present isogeometric formulation, the number of unknowns is independent of the number of layers. The proposed isogeometric formulation is validated by comparing the present results with the available published and the three-dimensional (3D) finite element results. In addition to correctly predicting the distribution of all stress components of the composite steel–concrete beams, the proposed formulation is computationally very economic.     

Long-term deflection of cracked composite beams with nonlinear partial shear interaction: I — Finite element modeling

In this paper, a uniaxial nonlinear finite element procedure for modeling the long-term behavior of composite beams at the serviceability limit state is presented. The finite element procedure follows a displacement-based approach. The nonlinear load-slip relationship of shear connectors as well as the creep, shrinkage, and cracking of concrete slab are accounted for in the proposed finite element procedure. The effects of creep and shrinkage of the concrete slab are considered only for uncracked concrete. The nonlinear iterative procedure adopted for tracking the nonlinear behavior of the composite beam implemented the total nodal deformations, not the incremental deformations, as the independent variables of any iteration. The results of the proposed finite element procedure were compared with the experimental results of four composite beams reported in the literature. The proposed finite element procedure was capable of predicting the deflections and stresses of the four beams with an acceptable degree of accuracy. A parametric study was conducted to study the effect of the nonlinearity of load-slip relationship of shear connectors and the cracking of the concrete deck on the long-term behavior of simply-supported composite beams.     

Finite element analysis and design of sandwich panels subject to local buckling effects

Past research into the local buckling behaviour of fully profiled sandwich panels has been based on polyurethane foams and thicker lower grade steels. The Australian sandwich panels use polystyrene foam and thinner and high strength steels, which are bonded together using separate adhesives. Therefore a research project on Australian sandwich panels was undertaken using experimental and finite element analyses. The experimental study on 50 foam-supported steel plate elements and associated finite element analyses produced a large database for sandwich panels subject to local buckling effects, but revealed the inadequacy of conventional effective width formulae for panels with slender plates. It confirmed that these design rules could not be extended to slender plates in their present form. In this research, experimental and numerical results were used to improve the design rules. This paper presents the details of experimental and finite element analyses, their results and the improved design rules.